Many of the founders of political party Agalev came from or were inspired by the social movement Agalev. This movement was founded by the JesuitLuc Versteylen, who had founded the environmental movement Agalev in the 1970s. Core values of this social movement were quiet, solidarity and soberness. This movement combined progressiveCatholicism with environmentalism. It sought to spread environmental consciousness first on a small scale, but since 1973 it took action to protect the environment and promote environmental consciousness. In the 1974 and 1977 elections Agalev supported several candidates from traditional parties, these however soon forgot the promises they made. In 1977 the movement entered the elections in several municipalities not to gain seats, but to promote its ideals.

In reaction to these broken promises, a debate erupted within Agalev on whether to set up a political party or to remain independent of politics. In the same year the party contested several municipal elections to no avail. A national level Agalev Working Group was founded to coordinate the new party. It also set up a separate association that could enter in elections. It participated in the 1979 European elections. Although the party won 2.3% of the votes, it won no seats.

In the 1981 election the party won 4% of vote and two seats in the Chamber of Representatives and one in the Senate. Ecolo, the Walloon green party also won two seats in the Chamber and three seats in the Senate. The political party Agalev was officially founded in 1982. It remained separate of the social movement. Prominent members of the movement Agalev, such as founder Versteylen chose not to join the political party Agalev. In the municipal elections of 1982 the party performed particularly well winning more than 10% in several municipalities. In its first periods in parliament the party functioned as a protest party forcing the other parties to take more action against environmental pollution and Third World poverty. The party campaigned on specific environmental issues, such as local anti-nuclear energy protests.

The party won two additional seats in the 1985 elections, two additional seats in 1987 and one in 1991: in that year it won seven seats in parliament. Agalev had become a serious political partner for other parties. In 1992 Agalev was asked to support a constitutional change called the Sint-Michiels accords, which would make Belgium a federation. Agalev gave its support in exchange of a tax on bottles, the first ecotax in Belgium. In the 1995 the party campaigned on a clean hands theme, after a series of political scandals was revealed. The party however lost two seats.

On the national level, the greens, both Ecolo and Agalev were able to enact legislation on several key green issues: the cabinet decided to opt out of nuclear energy, it opened marriage to homosexuals, legalized several thousands of illegal foreigners, enacted an anti-discrimination law and promised to in time spend 0,7% of the national income on development aid. On the Flemish level organic agriculture was promoted, people with handicaps got personal budgets and a system of time credits was enacted to allow people to combine work, care and free time better. The party however faced several crises. Magda Aelvoet left the federal cabinet in August 2002 over a cabinet decision to trade arms with Nepal, which was at civil war at the time. She was replaced by Jef Tavernier. The Ecolo minister for mobility Isabelle Durant left the cabinet just before the elections over the issue of nighttime airplane flights over Brussels. Finally the party voted in favour of a new election law that enacted a 5% Election threshold in both the Senate and the Chamber.

The 2003 federal election formed a turning point for the party. The party was reduced to 2,6% of the vote, well below the 5% limit and the party lost its seats in the Chamber and Senate. In response to the election results the Flemish ministers Mieke Vogels and Vera Dua stepped down. They were replaced by Adelheid Byttebier and Ludo Sannen respectively. The party renewed is its political profile and made some important strategic decisions. Agalev would continue as an independent Flemish progressive Green party. The party congress rejected the proposal of Agalev-Limburg to form a federal cartel with the SP.A and Spirit. The party also ruled out any participation in the future Flemish Government. The party would allow provincial and municipal cartels. The party changed its name to Groen!. The party changed the function of political secretary to party president, bringing the party more in line with other Belgian parties. Vera Dua became the first party president. The decision to continue separately led to considerable upheaval within the party, several prominent members, such as Antwerpen councillor Fauzaya Talhaoui and Flemish minister Sannen left the party and joined either Spirit or SP.A. Sannen was replaced as minister by Tavernier.

Before the 2004 elections Dua announced that if the party was supported by less than 280.000 votes, the independent green political project would end. The party gained enough support to meet this limit, although it lost half of it seats in Flanders compared to the 2000 elections. The party won seats in every provincial district except Limburg, where the support to cooperate with SP.A and Spirit was greatest.

In the 10 June 2007 federal election, the party regained representation in both the Chamber and the Senate. It got 265,828 votes (4% of total) and four seats.

The regional (for Flemish Parliament) and European elections of June 2009 were generally devoted to promote the concept of a green economy as an answer to the national and global economic crisis. The results of the election were below the expected and stranded on a status quo. Chairwoman Mieke Vogels chose to give up her presidency and was succeeded by Wouter Van Besien in October 2009.

On 11 January the Party unveiled its new logo and announced the dropping of its trademark exclamation point from the end of the party's name, after 8 years of usage. The new party slogan is "Works for all" to highlight the party's desire to look after the needs of all of society, not just its traditional voter base.

The party was founded as Agalev, which meant Anders Gaan Leven (English: to start living differently). This conveyed the green message that humans need to choose alternative lifestyles that are more sustainable. When the party registered at the election authority, it was forced to supply a meaning for each initial. The party thus ran under the name Anders Gaan Arbeiden, Leven, En Vrijen (English: going to work, live and have sex differently), improvised and not entirely serious, but legally correct.

After the 2003 election defeat the party renewed its political profile. This also involved a name change to Groen! (English: Green!). The name conveyed a closer alliance to the worldwide green movement with the word green and an independent and positive nature with exclamation mark.

In January 2012 the party underwent another name change by removing the exclamation mark from the end of its name.

As a traditional green party, the three core values of Agalev were ecology, peace and participatory democracy. In the early years the party specifically sought to overcome traditional cleavages (liberal-socialist, Catholic-secular and Flemish-Belgian). Since the 1980s the ideals of diversity and social justice have also taken a prominent role. The party now places itself explicitly in the left/progressive camp. In its current political program it connected these three values by the concept of quality of life.

In this table the election results of Agalev/Groen!/Groen in House of Representatives, Senate and European elections is represented, as well as the results of regional elections for Flanders and Brussels. The party's political leadership is represented as well. If it was part of the governing federal coalition, then its minister is listed.

The six biggest Flemish political parties and their results for the House of Representatives (Kamer). From 1978 to 2014, in percentages for the complete 'Kingdom'.

The support of Green! has strongly fluctuated recently. It draws most of its support from Flemish voters who do not feel bound to the strong social organizations and pillars. The party is strongest in urban areas with concentrated student populations like Ghent and Leuven.

Green!'s support is distributed in the following way between the electoral districts in the 2007 general election:

The highest organ of Green is the party congress, which is open to all members. The party has a relatively decentralized organization with strong municipal branches and a relatively small national organization. For a long time the party did not have a party president who set out the political strategy, but a party secretary with far less power. In 2003 the party changed this situation.

In contrast to other parties, Green MPs face relatively strong regulation: the party does not allow multiple offices per person, while it is traditional for Belgian MPs to be both mayor of municipality and federal MP for instance; furthermore MPs are not allowed to run for more than two terms; to ensure gender equality every second candidate on the party list has to be female; finally a high percentage of the income of MPs is taxed by the party.

By Belgian standards Green has relatively few members, ranging from 2,000 to 6,500. This is only about 1% of the Green voters. Generally Belgian parties have about 10% of their voter base as members.

The party's youth organization, Young Green (earlier Young Agalev), grew out of local groups of young Groen members, active since the late eighties and early nineties. These local groups started coordinated action in 1996. In 1998 Jong Groen was officially founded.

Green is ideologically and historically linked to the environmental movement Agalev, which was founded by the Jesuit Luc Versteylen. The party and the social movement are separate entities. Green still has strong contacts with environmental organizations. It has not developed a pillar of social organizations around it as other parties have.

The party has relatively good relations with the SP.A-SPIRITcartel. It was asked to join them in 2003, but it refused. Furthermore, the party has maintained good relations with its Walloon sister party, Ecolo.